Medical devices that can deliver biologically active agents such as drugs to a tissue are finding use in a wide variety of applications. For example, implantable medical devices (i.e., implants) that are capable of delivering drugs to an adjacent tissue can be designed to offer advantageous performance ranging from treatment of diseases to prevention of adverse reactions and/or rejection of the implant by the body. Implantable medical devices are typically designed with a profile for releasing biologically active agents at a specified rate over a desired period of time.
For some applications it is desirable that an implantable medical device be capable of a nearly constant rate of release of biologically active agent (e.g., a therapeutic agent) over a sustained period of time (i.e., sustained release). Frequently such medical devices include a solvent-based coating that may optionally include the biologically active agent, with the coating being capable of modulating and/or controlling the release profile of the biologically active agent. However, application of such solvent-based coatings can be problematic, for example, in that the solvent may have an adverse effect on the medical device, particularly when the medical device includes polymeric material that can be softened or dissolved by the solvent. Further, the solvent can also have an adverse effect on the biologically active agent itself, particularly when the biologically active agent is a protein-based drug. Moreover, damage that may occur to a coated medical device while making or using the device can adversely affect the ultimate performance of the device.
There is a continuing need for new medical devices that are capable of releasing biologically active agents, and methods of making such devices.